Casing centralizer



y 24, 1951 E. H. CLARK, JR

CASING CENTRALIZER Filed oct. l, 1948 INVENTOR.

s m i Q m n L E B Patented July 24, 1951 CASING CENTRALIZER' Earnest H. Clark, Jr., Long Beach, Calif., assignor to Baker Oil Tools, Inc.-, Vernon, Calif., a corporation of California,v

Application-October 1, 1948; Serial No. 52,303

16 Claims.

The present invention relates to centering detibns on the sizebore hole: in which they canv be used. They: cannot be employed in so-called 'sl-im "ho1es-of only slightly greater diameter than the diameter of the casing on which they are-mounted. In additiomprior devices have. not permitted the well casingtoi be rotated. in the well bore without rotating the centering device, unless the effective minimum: diameter of the device is made so. large as: to prevent. its. use: in

'-s1im'holes. I

Accordingly, it is an object of the present in.- vention. to provide a. casing. centering device which can. be; collapsed inwardly to a comparatively small effective external diameter, and which. allows the casing. to be rotated, without :rotatingthe-centering,device-itself. I

Another object of the invention is to provide a casing centering device embodying outwardly bowed spring-s capable of being collapsed inwardly toa comparatively small effective diameter and ofbeing pulled through a well bore, the centering device allowing the casing to be rotated without rotating the device itself.

A further object. of the invention is to provide a: casing centralizer that can be easily assembled and. placed in operative position on acasing section, or similar conduit, which has an over-all relatively small minimum efiective diameter, and which allows the casing to be rotated within it.

Thisinvention possesses many other advantages, and has other objects. which may bev made more clearly apparent from a consideration of a form in which it may be. embodied. This form is shown in the drawings. accompanying and forming- -part of the presentspecification. It will now' be described in detail, for. the purpose of illustrating the general principles of the invention; butit is to be understood thatsuch detailed descriptionis not to be takenin a limi-tingsense, since the scope of the invention: is best defined bythezappendedclaims.

Referring to the drawings:

Figure 1. is. a. side elevation of a. centralizer mounted on a casing section, with the springs occupying.- their maximum outward position;

Fig. 2is. avlew, similar to Fig. 1, of the device disposed inawell bore;

Fig. 3 is a cross-section through taken along line 33 of Fig. l; and

Fig- 4 is; a cross-section taken along the line 4-4 oILFig. 1.

Thecasing centering device A ismounted on a casing: section, liner or similar conduit B adapted to berun in a bore hole C. As is well known. the purpose of centering, devices is to dispose the casing Brcentrallyoi the bore hole C.

The centering device disclosed in the drawings includes a plurality of circumferentially spaced. outwardly bowed leaf springs l0. whose upper and lower ends are attached to upper and lower collars H, 12,. respectively, that are slidable upon the casing section B. The ends [3 of the springs abut the inwardly facing ends I4, l5 of. the collars,v towhich they are butt welded. An efiicient weld can be made through use of anatomic hydrogen arc, a bead 16 running along the abutting ends of the collar and each spring, which projects. but little. if at all, beyond the outer adjacent surfacesof the collar and. spring. Thethicke ness of the springs I0 is approximately equal to,

the centralizer,

.andispreferably no greater than, the thickness of the collars ll, 12, to hold the effective diameter across the springs to a minimum extent, when they are collapsed inwardly against the casing B by the fullest amount. 7 Rings l1, l8 are disposed above the-upper collarzll and below the lower collar I2, each ring being secured in spaced relation with respectto its adjacent collar by a plurality of circumferentially spaced connecting elements [9, which. may be in the form of relatively short bandsor straps engaging the periphery of the collar and ring, and welded thereto, as by running a bead 20 around the edges of the connecting element H) which overlap the-ring and collar. I

The inside and outside diameters ofthe rings ll, l8 are. substantially the same as. the inside andOutside diameters of the collarsl l', [2;1whe'reas the thickness. of the connecting elements. [9 may be substantially less than the thickness of the collars andrings, since these connectingelements are only subjected to a tensile pull or strain, as-hereinafter described.

,Longitudinally spaced. holes 2| may be provided-in each connecting element 19" to facilitate assembly. ,of the centralizer. parts, and welding of the connecting elements I9 to the collars II, I2 and the rings IT, IS, with each ring spaced from its adjacent collar by a predetermined amount. Pins (not shown) may extend through the holes 2! in the connecting straps, and the opposing ends of a collar and ring at each end of the casing centralizer placed in engagement with these pins, whereupon the straps I9 can be welded to the peripheries of the collar and ring, as indicated above, and the pins then removed.

The casing centralizer A may be placed upon a casing section B that is to form part of a casing string to be disposed in a well bore. After being placed on the casing section, circumferentially spaced stop members 22, in the form of lugs, are placed through the arcuate spaces between the connecting elements I9 into engagement with the edge of each stop ring which is opposed to its adjacent collar. That is, the stop members or lugs 22 are placed in engagement with the lower end 23 of the upper ring I7 and with the upper end 24 of the lower ring I8. These lugs are then welded to the casing section, as by depositing welding material 25 within a hole 26 in each lug 22, which integrates the latter to the casing section B.

It is to be noted that both the upper and lower sets of lugs 22 engage the stop rings I'I, I8 when the outwardly bowed springs III are unconfined, and that there is substantial distance between each set of lugs and the adjacent collar member II or I2 (Fig. 1). The lugs 22 are preferably thinner than the collars II, I2 and rings l1, l8, so that they do not project beyond the peripheries of the latter and will not engage the interconnecting strap elements I9.

When the casing centr-alizer has been assembled on the casing section B with the stop members 22 welded in place, as illustrated in Fig. l, the casing section B may be connected to the other sections constituting the casing string, and the latter lowered through the well bore. During this lowering operation, the lower set of lugs 22 engages the lower ring I8 and exerts a pulling action on the interconnecting straps I9 and lower collar I2, which is transmitted to the bowed springs I 0, in order to pull these springs through the well bore. Such pulling action facilitates inward collapsing of the outwardly bowed springs II] to a minimum eifective diameter. During such inward collapsing, the upper collar II, ring I! and straps I9 are shifted upwardly along the easing (Fig. 2). However, such upward shifting can occur without interference from the upper stop lugs 22 welded to the casing section, since sufiicient space is allowed between these members 22 and the upper collar I I when the centering device is assembled on the casing section, as is evident from Fig. 1.

Similarly, upward movement of the casing string B causes the upper set of stop members 22 to engage the upper ring IT, to exert the pulling action on the straps I9 and outwardly bowed springs ID, in order to facilitate their passage through restrictions in the well bore, Without buckling and breaking. During such upward movement, the lower collar I2 may shift toward the lower set of stop members 22 without interference, in view of the initial space allowed therebetween.

The minimum diameter of well bore C through which the casing centralizer A can pass is determined by the extent that the interconnecting strap elements 19 project beyond the peripheries of the collars Il, I2 and rings I1, I8. Since these straps have only a, tensile load imposed upon them, they can be made of comparatively thin metal. Their thickness is much less than the thickness of the collars and rings themselves. Accordingly, the minimum effective diameter of the casing centralizer is but very little more than the external diameter of the collars and rings themselves.

There are no elements disposed within the outwardly bowed springs II} which will deter or interfere with their complete collapsing against the casing section. Accordingly, the centering device can be run in well bores, such as slim holes, that have only a slightly greater diameter than the full collapsed diameter across the outwardly bowed springs.

It is also to be noted that the arrangement allows the casing string B to be rotated within the casing centralizer A, and without rotating the latter. This latter action, if it occurred, would drag the springs IE] around the wall of the well bore, scraping drilling mud and formation material from the latter, and also possibly damaging the springs. There are no elements in the present casing centralizer interfering with rotation of the casing section within the centering device. The stop members 22 can slide freely along the stop rings I7, I8 and collars I I, I2, and since they do not project beyond the periphery of the stop rings and collars, they can pass freely under the interconnecting strap elements [9.

It is, accordingly, apparent that a simple and inexpensive casing centralizer has been provided, capable of. use in slim holes, and in which the outwardly bowed springs Ii are pulled through the well bore upon longitudinal movement of the casing string through the well bore in both directions. In addition, the casing string can be rotated without rotating the casing centralizer.

The inventor claims:

1. A centering device; including a pair of longitudinally spaced generally cylindrical members; circumferentially spaced outwardly bowed springs having their end portions fastened to said members; a ring spaced longitudinally outwardly from each member; means securing each ring and member together in spaced relation; and stop means disposed between each ring and its adjacent member and engageable with the inner end of said ring to exert a pulling action on said springs.

2. A centering device; including a generally cylindrical member; circumferentially spaced outwardly bowed springs having their end portions fastened to said member, said springs extending from said member in one longitudinal direction; a ring secured to said member and spaced longitudinally therefrom in a direction opposite from the direction in which said springs extendfrom said member; means securing said ring and member together in spaced relation; and stop means disposed between said member and ring and engageable with the inner end of said ring to-exert a pulling action on said springs.

3. A centering device; including a pair of longitudinally spaced generally cylindrical members; circumferentially spaced outwardly bowed springs having their end portions fastened to said members; a ring spaced longitudinally outwardly from each member; means secured to the exteriors of each ring and member for securing said ring and member together in spaced relation; and'stop means disposed between each ring and its adjacent member and engageable with the inner end of saidring to exert a pulling action on 'said springs. r

I L-A centering device; including-a generally cylindrical member; circumferentially spaced outwardly bowed springs having their end portions fastened to said member, said springs extending from said member in one longitudinal direction; a'ring spaced longitudinally from said member inthe direction opposite to the direction in which said springs extend from said members; means secured to the exteriors of said ring and member for securing them together in spaced relation; and stop means disposed between said member and ring and engageable with the inner end of said-r-ingto exert a pulling action on said springs.

5. A centering device as defined in claim 3; in Which-said stopmeans do not extend beyond the peripheries of said members and rings.

6. A centering device as defined in claim 4; in whichsaid stop means does notextendbeyond the peripheries of said member and ring.

7. A centering device; including a pair of longitudinally spaced generally cylindrical members; circum-ferentially spaced outwardly bowedsprings fastened to said members; a ring spaced longitudinally outwardly from each member; circumferentially spaced straps engaging the exteriors of each member and its associated ring and secured to said member and ring; and stop means disposed between each ring and its adjacent member and engageable with the inner end of said ring to exert a pulling action on said springs; said stop means extending outwardly no further than the peripheries of said members and rings.

8. A centering device; including upper and lower spaced generally cylindrical members; circumferentially spaced outwardly bowed springs disposed between said members with their upper and lower end portions substantially abutting and secured to the inner portions of said upper and lower members, respectively; an upper ring disposed in spaced relation above said upper member; a lower ring disposed in spaced relation below said lower member; circumferentially spaced straps Welded to the exteriors of said upper member and upper ring; circumferentially spaced straps welded to the exteriors of said lower member and lower ring; stop means disposed between said upper member and upper ring and engageable with the inner edge of said upper ring; and stop means disposed between said lower member and lower ring and engageable with the inner edge of said lower ring.

9. In combination with a casing; upper and lower longitudinally spaced generally cylindrical members slidable on said casing; circumferentially spaced outwardly bowed springs disposed between said members with their upper and lower end portions substantially abutting and secured to the inner portions of said upper and lower members, respectively; an upper ring slidable on said casing and disposed in spaced relation with and above said upper member; a lower ring slidable on said casing and disposed in spaced relation with and below said lower member; circumferentially spaced straps welded to the exteriors of said upper member and upper ring; circumferentially spaced straps welded to the exteriors of said lower member and lower ring; stop means secured to said casing between said upper member and upper ring and engageable with the lower edge of said upper ring; and stop means secured to said casing between said lower member and lower ring and engageable with the upper edge of said lower ring.

10. .A centering device: including a generally cylindrical member; circumferentially spaced outwardly bowed springs having their end portions fastened to said member, said springs extending from said member in one longitudinal direction; a ring spaced longitudinally from said member in the direction opposite to the directionin which said springs extend from said member; circumferentially spaced straps engaging the exteriors of and secured to said member and ring forsecuring them together in spaced relation; and stop means disposed between said member and ring andengageable with the inner end of said ring to exert a pulling action on said springs, .said stop means extending outwardly no further than the peripheries of said member and ring so as to. avoid engagement with said straps,

11. Acentering device; including a generally cylindrical member; circumferentially spaced outwardly bowed springs having their end portions fastened to said member, said springs extending from said member in one longitudinal direction; a ring spaced longitudinally from said member in the direction opposite to the direction in which said springs extend from said member; circumferentially spaced straps out of alignment with said springs, said straps engaging the exteriors of and secured to said member and ring for securing them together in spaced relation; and stop means disposed between said member and ring and engageable with the inner end of said ring to exert a pulling action on said springs, said stop means extending outwardly no further than the peripheries of said member and ring so as to avoid engagement with said straps.

12. A centering device: including a generally cylindrical member; circumferentially spaced outwardly bowed springs having their end portions fastened to said member, said springs extending from said member in one longitudinal direction, the end portions of said springs extending laterally outward no further than the periphery of said member; a ring spaced longitudinally from said member in the direction opposite to the direction in which said springs extend from said member; means secured to the exteriors of said ring and member for securing them together in spaced relation; and stop means disposed between said member and ring and engageable with the inner end of said rin to exert a pulling action on said springs.

13. A centering device: including a generally cylindrical member; circumferentially spaced outwardly bowed springs having their end portions fastened to said member, said springs extending from said member in one longitudinal direction, the end portions of said springs extending laterally outward no further than the periphery of said member; a ring spaced longitudinally from said member in the direction opposite to the direction in which said springs extend from said member; circumferentially spaced straps out of alignment with said springs, said straps engaging the exteriors of and secured to said member and ring for securing them together in spaced relation; and stop means disposed between said member and ring and engageable with the inner end of said ring to exert a pulling action on said springs, said stop means extending outwardly no further than the peripheries of said member and ring so as to avoid engagement with said straps.

14. A centering device: including a pair of Iongitudinally spaced generally cylindrical members; circumferentially spaced outwardly bowed springs having their end portions fastened to said members; a ring spaced longitudinally outwardly from each member; circumferentially spaced straps out of alignment with said springs, said straps engaging the exteriors of each member and its associated ring and secured to said member and ring; and stop means disposed between each ring and its adjacent member and engageable with the inner end of said ring to exert a pulling action on said springs; said stop means extending outwardly no further than the peripheries of said members and rings.

15. A centering device: including a pair of Iongitudinally spaced generally cylindrical members; circumferentially spaced outwardly bowed springs having their end portions fastened to said members, said end portions extending laterally outward no further than the peripheries of said members; circumferentially spaced straps engaging the exteriors of each member and its associated ring and secured to said member and ring; and stop means disposed between each ring and its adjacent member and engageable with the inner end of said ring to exert a pulling action on said springs; said stop means extending outwardly no further than the peripheries of said members and rings.

ring and secured to said member and ring; and.

stop means disposed between each ring and its adjacent member and engageable with the inner end of said ring to exert a pulling action on said springs; said stop means extending outwardly no further than the peripheries of said members and rings.

EARNEST H. CLARK, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,089,553 Hartman et al Aug. 10, 1937 2,228,648 Welles Jan. 14, 1941 2,228,649 Welles Jan. 14, 1941 

